The invention relates to a honeycomb body configuration including a honeycomb body having a fluid inlet side and a fluid outlet side, in particular a catalyst support structure for motor vehicles, formed of at least partially structured layers of sheet metal which, after being stacked and/or wound, form channels through which a fluid can flow. The honeycomb body is surrounded by an inner tubular jacket and an outer tubular jacket provided concentrically thereto. At least an axial subregion of the inner tubular jacket is configured as a corrugated tube.
Honeycomb body configurations of this type are known per se. Published, Non-Prosecuted German Patent Application No. DE 2 300 704 describes, for example, ceramic honeycomb bodies having a metallic layer on their surface. Connected to this layer are elastic elements which, for their part, are mounted in turn in the outer tubular jacket. The elastic holding elements are, in particular, sections of corrugated tube which are intended to absorb the thermally induced relative movements between the honeycomb body and the outer tubular jacket. The elastic elements are provided either in two parts, in each case on the fluid inlet side and fluid outlet side, or in one part, over the overall length of the honeycomb body, and each have a flange for connection to a pipeline.
Also for metallic honeycomb bodies which are constructed of layers of sheet metal it is known, for example from Published, Non-Prosecuted German Patent Application DE 39 41 642 A1, for the purpose of preventing stresses due to thermal expansion, to surround layers of sheet metal with an outer metal tubular jacket having short corrugations at a short distance apart, with the result that a honeycomb body having an outer tubular jacket of this type is able to expand and shrink.
In the case of honeycomb body configurations having an inner and an outer tubular jacket which, at least in subregions, are intended to be displaceable relative to each other, there are also a large number of problems involving the manufacture because particularly when brazing or welding connections it has to be ensured in each case that undesirable additional connections between the two tubular jackets do not obstruct the mutual displaceability.
It is accordingly an object of the invention to provide a honeycomb body configuration which overcomes the above-mentioned disadvantages of the heretofore-known configurations of this general type and which can be produced in a reproducible manner with uniform quality and ensures, by providing a good equalization of mechanical and thermal loads, a permanent and secure mounting of a honeycomb body constructed from layers of sheet metal in a metallic housing, even under special operating loads. It is a further object of the invention to achieve a good cold-starting performance of a catalytic exhaust gas cleaning device having the honeycomb body configuration according to the invention.
With the foregoing and other objects in view there is provided, in accordance with the invention, a honeycomb body configuration, including:
a honeycomb body formed of at least partially structured sheet metal layers, the at least partially structured sheet metal layers being stacked sheet metal layers and/or wound sheet metal layers and defining channels for a fluid to flow
therethrough, the honeycomb body having a fluid inlet side and a fluid outlet side;
an inner tubular jacket surrounding the honeycomb body;
an outer tubular jacket provided concentrically with respect to the inner tubular jacket and surrounding the honeycomb body;
the inner tubular jacket having a first longitudinal subregion and at least a second longitudinal subregion, the first longitudinal subregion having a first length including a first partial length, the second longitudinal subregion having a second length including a second partial length;
the inner tubular jacket being configured, in the first longitudinal subregion, as a corrugated tube having tubular corrugations such that the first longitudinal subregion is a corrugated subregion;
the second longitudinal subregion being a smooth subregion bearing flat against the honeycomb body;
the smooth subregion and the honeycomb body being joined at least at the second partial length; and
several of the tubular corrugations provided next to one another and the outer tubular jacket being joined at the first partial length, the first partial length being dimensioned for a conventional joining connection.
In other words, the honeycomb body configuration according to the invention includes a honeycomb body having a fluid inlet side and a fluid outlet side, in particular a catalyst support structure for motor vehicles, formed of at least partially structured layers of sheet metal which, after being laminated and/or wound, form channels through which a fluid can flow, the honeycomb body being surrounded by an inner tubular jacket and an outer tubular jacket provided concentrically thereto, and at least an axial subregion of the inner tubular jacket being configured as a flexible corrugated tube, having tubular corrugations, the inner tubular jacket having at least one further axial subregion which bears smoothly against the honeycomb body, and the smooth subregion and the honeycomb body being at least partially connected axially to each other by a join, a plurality of tubular corrugations provided next to one another of the corrugated subregion and the outer tubular jacket are partially connected axially to one another by a join, each corrugated subregion provided for connection to the outer tubular jacket by a join being dimensioned in its partial length such that conventional connecting methods, in particular soldering and/or welding processes, can be used.
Mechanical and thermal loads can be equally well equalized and a permanent and secure mounting configuration of the honeycomb body in the housing ensured in an advantageous manner by the inner tubular jacket of the honeycomb body having, in addition to an axial or longitudinal subregion configured as a flexible corrugated tube, having tubular corrugations, at least one further axial or longitudinal subregion which bears smoothly (flat) against the honeycomb body, and by a plurality of tubular corrugations provided next to one another of the corrugated subregion and the outer tubular jacket being partially connected to each other axially by a join, and by the smooth subregion and the honeycomb body being at least partially connected to each other axially by a join. According to the invention, each corrugated subregion provided for connection to the outer tubular jacket by a join is dimensioned in its partial length in such a manner that conventional connecting methods, in particular brazing and/or welding processes, can easily be used.
According to the invention, the honeycomb body configuration is preferably distinguished in that first of all a smooth subregion is provided on the fluid inlet side, followed by at least one corrugated subregion and at least one further smooth subregion, thereby resulting in a total of n corrugated subregions and n+1 smooth subregions, n being an integer and being greater than or equal to 1. By providing, on the fluid inlet side, a smooth subregion acting as an air-gap insulation, rapid starting of the catalytic reaction when beginning to be subjected to exhaust gas to be cleaned is ensured in an advantageous manner. As an alternative to the air-gap insulation, the thermal insulation can also be improved through the use of an insulating mat, for example made of ceramic material, which has very low heat-conducting and heat-convection properties.
In one particular embodiment, where n=1, the one corrugated subregion is predominantly provided on the fluid inlet side. As a result, the smooth section of the inner tubular jacket on the inlet side is only short, for example 5 to 25 mm, and in particular the mechanical loads on the fluid inlet side which are caused by exhaust gas strongly pulsating from time to time are absorbed in an advantageous manner.
Alternatively, in another embodiment, for n=1, the one corrugated subregion can be provided centrally axially, i.e. essentially in the center of the honeycomb body, as seen in the axial direction. This has the advantage of not having to pay attention to the installation direction during assembly.
Alternatively, for n=1, the one corrugated subregion can also be predominantly provided on the fluid outlet side, in particular if a long, smooth, first subregion is desired in order to obtain a large volume, insulated from the outer tubular jacket, in the honeycomb body.
For n=2, one corrugated subregion is provided behind a smooth subregion on the fluid inlet side and another corrugated subregion is provided in front of a smooth subregion on the fluid outlet side. A mounting configuration of this type on both sides, i.e. on the fluid inlet side and fluid outlet side, of the honeycomb body in the outer tubular jacket is particularly advantageous in terms of equalizing mechanical loads and has the effect of the honeycomb body being supported in a manner which is very insensitive to vibrations.
For n=3, the first corrugated subregion is provided on the fluid inlet side, the second corrugated subregion is provided centrally axially, and the third corrugated subregion is provided on the fluid outlet side, in each case alternating with smooth subregions. A configuration of this type combines the advantages which have already been demonstrated even in honeycomb body configurations subjected to extreme loading, for example ones installed near to the engine. For n greater than 3, the corrugated and smooth subregions are provided analogously to the previous configurations.
According to another feature of the invention, in the case of a central axial configuration of one corrugated subregion, only this corrugated subregion is partially connected axially to the outer tubular jacket by a join.
According to yet another feature of the invention, in the case of a central axial configuration of one corrugated subregion, the smooth subregions in each case provided adjacently, or the smooth subregions in each case provided on the fluid inlet side and the fluid outlet side are at least partially connected axially to the honeycomb by a join.
According to another feature of the invention, in the case of a predominantly or exclusively decentralized axial configuration of the corrugated subregion/subregions, the latter is/are partially connected axially to the outer tubular jacket by a join only on the fluid inlet side and/or on the fluid outlet side.
According to a further feature of the invention, in the case of a predominantly or exclusively decentralized axial configuration of the corrugated subregion/subregions, the smooth subregion/subregions which is/are provided centrally axially, on the fluid inlet side or on the fluid outlet side, is/are at least partially connected axially to the honeycomb by a join.
According to yet another feature of the invention, each smooth subregion provided for a connection to the honeycomb by a join is dimensioned in its partial length in such a manner that conventional connecting methods, in particular brazing and/or welding processes, can be used.
To obtain a durable connection, the inner tubular jacket has to be connected to the honeycomb body at least in one region and to the outer tubular jacket in one region. It is preferred if all smooth subregions are at least partially connected, in particular brazed or hard-soldered, to the honeycomb body. In addition, it is preferred if all corrugated subregions are connected, preferably likewise brazed or hard-soldered or welded, to the outer tubular jacket. In this configuration, however, it is important not to connect all of the crests of the corrugations to the outer tubular jacket, since otherwise the effect of the corrugations as a compensator for expansion would be obstructed. At least some of the crests of the corrugations are to remain unconnected, in particular two crests of the corrugations which are adjacent on both sides to a smooth subregion of the inner tubular jacket are not to be connected to the outer tubular jacket.
In a preferred embodiment, the sum of the axial lengths of the corrugated subregions amounts to more than half, preferably to more than two thirds, of the overall length of the honeycomb body. This advantageously facilitates the equalizing of mechanical loads, in particular.
In one particular embodiment, the tubular corrugations of the corrugated subregions have, viewed over their longitudinal axial section, very steep flank regions, in particular even an omega shape. Such a refinement of the tubular corrugations ensures, in each case depending on the thermal load, load-adapted expansion and shrinking of the inner tubular jacket.
Irrespective of their remaining shape, the tubular corrugations are preferably of flattened configuration in the region of their connection to the outer tubular jacket by a join. Flattened regions of this type enable a flat connection which withstands high mechanical and thermal loads.
The partial connection between a corrugated subregion and the outer tubular jacket by a join therefore extends in each case over 1 to 5, preferably over 2 to 4, in particular over 3, crests of the tubular corrugation of the corrugated subregion, with the result that the connections can be produced permanently and securely by the manufacturing process in accordance with their use.
According to the invention, the ratio of tubular corrugations connected by a join to tubular corrugations not connected by a join is preferably at most 1:1.5, preferably 1:4, so that equalization in particular of mechanical loads is ensured.
The first smooth subregion provided on the fluid inlet side is at least 5 mm long, preferably at least 7.5 mm, in particular approximately 10 mm, the other smooth subregions are at least 15 mm long, preferably at least 20 mm, in particular approximately 25 mm.
The honeycomb body, which is, in particular, a catalyst support structure through which a flow can take place axially, can have any desired geometrical, preferably a cylindrical or a conical, shape.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a honeycomb body configuration, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.